Use of renewable oil in hydrotreatment process

ABSTRACT

The use of bio oil from at least one renewable source in a hydrotreatment process, in which process hydrocarbons are formed from said glyceride oil in a catalytic reaction, and the iron content of said bio oil is less than 1 w-ppm calculated as elemental iron. A bio oil intermediate including bio oil from at least one renewable source and the iron content of said bio oil is less than 1 w-ppm calculated as elemental iron.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. patentapplication Ser. No. 14/932,566, filed Nov. 4, 2015, now U.S. Pat. No.9,969,940 issued May 15, 2018, in turn, to U.S. patent application Ser.No. 14/273,024, filed May 8, 2014, now U.S. Pat. No. 9,206,092 issuedDec. 8, 2015, in turn, to U.S. patent application Ser. No. 13/397,236,filed Feb. 15, 2012, now U.S. Pat. No. 8,742,185 issued Jun. 3, 2014, inturn, to U.S. Provisional Application No. 61/443,161 filed Feb. 15,2011, the entire contents of which are herein incorporated by reference.U.S. patent application Ser. No. 13/397,236 also claims the benefit ofpriority under 35 U.S.C. § 119 to European Patent Application No.11154437.5 filed in Europe on Feb. 15, 2011, the entire contents ofwhich are herein incorporated by reference.

FIELD

Disclosed is the use of renewable oil in a hydrotreatment process, forexample, for the production of hydrocarbons. Also disclosed is the useof renewable oil comprising less than 1 ppm of iron, for the productionof liquid fuel components or components which can be converted to liquidfuels.

BACKGROUND INFORMATION

Liquid fuel components are mainly based on crude oil. There is an evergrowing demand for liquid fuels with lower CO₂ emissions compared tocrude oil based fuels. Various renewable sources have been used asalternatives for crude oil fuels. Methods for converting biomass toliquid fuels include transesterifications of triglycerides toalkylester, hydrotreatment of oils and fats to paraffins, and renewablediesel obtained through gasification and the Fischer-Tropsh process. Oneof the most promising and furthest developed method is hydrogenation ofvegetable oil (HVO) or animal fats to produce paraffins, which canfurther be refined, e.g., through isomerisation reactions to renewablediesel with excellent properties.

Vegetable oils and animal based fats can be processed to decompose theester and/or fatty acid structure and to saturate the double bonds ofthe hydrocarbon backbone thus obtaining about 80-85% of n-paraffinsrelative to the mass of the starting material. This product can bedirectly used as a middle distillate fuel component. The cold flowproperties of n-paraffins can be enhanced in an isomerisation step whereiso-paraffins are formed. A method of producing iso-paraffins fromvegetable oils and animal fats is presented in European Patent DocumentNo. EP 1 396 531.

Certain impurities present in the renewable oil can be harmful for theperformance of the hydrotreatment/deoxygenation catalyst. Triglyceridescan be converted to hydrocarbons through a hydrodeoxygenation pathwayusing classical hydrodesulphurisation (HDS) catalyst such as NiMo andCoMo HDS catalysts. However, the catalyst has been shown to bedeactivated as a result of phosphorous in the feedstock. In publicationKubicka et al (2010) it is shown that elimination of phosphorous fromthe feedstock is crucial to prevent rapid catalyst deactivation.

U.S. Patent Application Publication No. 2007/0010682 discloses a processfor the production of diesel range hydrocarbons from bio oils and fats,which method includes hydrodeoxygenation and hydroisomerisation toachieve fuel components with excellent performance. It is alsoacknowledged that in order to avoid catalyst deactivation and undesiredside reactions the amount of alkali metals and alkaline earth metals areless than 1 w-ppm calculated as elemental metal and phosphorus contentless than 5 w-ppm. Degumming and bleaching are suggested to remove theimpurities from the feed. In bleaching the refined oil feed is heatedand mixed with natural or activated bleaching clay to remove impuritiessuch as chlorophyll, phosphoric compounds and metals remaining in theoil after degumming.

There exist numerous commercial bleaching clays, which can be used inthe bleaching of renewable oils. European Patent Document No. EP 0 507217 discloses a porous base-treated inorganic adsorbent for removal ofcontaminants such as free fatty acids and metals from glyceride oils.The adsorbent is capable of reducing the levels of phosphorus to below0.3 ppm and the level of metals to below 0.1 ppm.

In previous laboratory scale experiments it has been shown thattriglycerides, e.g., in vegetable oils can be converted to hydrocarbonsin hydrotreatment reactions. However, in large scale production ofhydrotreated vegetable oil some difficulties have occurred over time. Asignificant increase in the pressure drop over the hydrodeoxygenationcatalyst bed was observed. In normal running conditions there is ahigher pressure at the top of the catalyst bed compared to the pressureat the bottom of the catalyst bed and this difference is called thepressure drop. The pressure drop drives the feed stream forward in thereactor. Over time, continuous plugging of the catalyst increases thepressure drop and could lead to complete plugging of the flow in thecatalyst bed. An increase in the pressure drop was observed after someproduction time even if the feed contained only trace amounts ofphosphorous and metal impurities such as Na, Ca and Mg.

These findings indicate that the hydrotreatment of glyceride oils fromrenewable sources still needs improvements and especially large scaleproduction encounters problems which could not have been foreseen fromthe early laboratory scale experiments.

SUMMARY

According to an exemplary aspect, disclosed is a method for preparing ahydrocarbon, the method comprising: subjecting a bio oil from at leastone renewable source to a hydrotreatment process, wherein in thehydrotreatment process, hydrocarbons are formed from said bio oil in acatalytic reaction employing a catalyst, wherein an iron content of saidbio oil is less than 1 w-ppm calculated as elemental iron.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the pressure drop over the catalyst bed in relation to thecumulative feed, in accordance with an exemplary aspect.

FIG. 2 shows the correlation between absolute increase in pressure dropand absolute masses of P and Fe found in the dust, in accordance with anexemplary aspect.

FIG. 3 shows the correlation between rate of increase in pressure drop(in bar/kg (feed) and concentrations of P and Fe in the feed, inaccordance with an exemplary aspect.

DETAILED DESCRIPTION

Disclosed is the use of bio oil from at least one renewable source, in ahydrotreatment process, in which process hydrocarbons are formed in acatalytic reaction and the iron content of the bio oil is less than 1w-ppm, for example, less than 0.5 and, for example, less than 0.25 w-ppmcalculated as elemental iron. The use of bio oil with extremely lowcontent of iron can be employed to reduce or avoid plugging of thecatalyst used in the hydrotreatment reaction.

An exemplary embodiment relates to the use of a glyceride oil from atleast one renewable source in a hydrotreatment process, in which processhydrocarbons are formed in a catalytic reaction and the iron content ofthe glyceride oil is less than 1 w-ppm, for example, less than 0.5 w-ppmand, for example, 0.25 w-ppm calculated as elemental iron.

The hydrotreating catalyst was found to be plugged, for example, inlarge scale production over a certain time. The particles responsiblefor the plugging of the catalyst were found upon analysis to containhigh amounts of phosphorous and metals. Further studies lead to thesurprising finding that the iron content of the feed used in thehydrotreatment process is responsible for the plugging of the catalyst.An exemplary aspect therefore relates to renewable oil with very lowiron content as the starting material for a hydrotreatment process.

Renewable oil enables longer running time of hydrotreating catalystswithout plugging. Previous studies have established that impurities suchas phosphorous and Na, Ca and Mg metals present in the feedstock may beresponsible for deactivation of the catalyst. An exemplary aspect canaddress the problem of catalyst plugging and ensure smooth running ofthe process and stable reaction conditions allowing manufacture ofhydrocarbons from glyceride oil with high conversion rate and highselectivity.

In addition, an exemplary aspect can prevent the hydrotreating catalystfrom deactivation, or reduce the degree of deactivation, and the lowamount of Fe in the oil minimises the oxidation of the renewable oil.Iron compounds can act as oxidants.

Here, bio oil is understood to mean any oil originating from a renewable(bio) source, including, for example, vegetable, animal or microbialsources. Bio oils can comprise at least fatty acids or fatty acidderivatives such as glycerides, alkyl esters of fatty acids, fatty acidalcohols or soaps.

Here, glyceride oil is understood to mean any oil which comprisestriacylglycerides. The glyceride oil may also comprise di- andmonoacylglycerides as well as fatty acids and their derivatives such asalkyl esters especially methyl esters. The chain length of thehydrocarbon chains in the glyceride oil can be from at least C8 up toC24. The term glyceride oil is meant to include at least, but notlimited to rapeseed oil, colza oil canola oil, tall oil, sunflower oil,soybean oil, hempseed oil, cottonseed oil, corn oil, olive oil, linseedoil, mustard oil, palm oil, peanut oil, castor oil, coconut oil,camellia oil, jatropha oil, oils derived from microbial sources, whichare possible genetically modified and includes at least algae, bacteria,moulds and filamentous fungi; animal fats, fish oil, lard, tallow, trainoil, recycled fats from the food industry and any mixture of the oils.

Here, oil from renewable source or renewable oil is understood to meanany oil originating from a source that can be considered renewable,i.e., not fossil. Renewable sources include at least all plant(vegetable) and animal based sources, but also microbial based sourcessuch as algae, bacteria, moulds and filamentous fungi etc. Re-use ofspent oil from food industry is also considered a renewable source aswell as oils obtained by conversion of wastes, such as municipal andslaughterhouse wastes.

Here the term hydrotreatment includes at least hydrodeoxygenation (HDO)and is understood as a collective term for all catalytic processes,which removes oxygen from organic oxygen compounds in the form of water,sulphur from organic sulphur compounds in the form of dihydrogensulphide (H₂S), nitrogen from organic nitrogen compounds in the form ofammonia (NH₃) (hydrodenitrogenation, HDN) and halogens, for examplechlorine from organic chloride compounds in the form of hydrochloricacid (HCl) (hydrodechlorination, HDCl), for example, under the influenceof sulphided NiMo or sulphided CoMo catalysts. Hydrotreatment is hereunderstood to include also decarboxylation/decarbonylation, i.e.,removal of oxygen in the form of COx.

Hydroisomerisation or isomerisation is here understood to mean anyprocess in which branches on the hydrocarbon backbone are formed andisoparaffins are produced. For example, methyl and ethyl side-chains areformed in the isomerisation step.

Disclosed is the use of bio oil, for example, glyceride oil, from atleast one renewable source in a hydrotreatment process, in which processhydrocarbons are converted from the bio oil in a catalytic reaction andthe iron content of the bio oil is less than 1 w-ppm, for example, lessthan 0.5 w-ppm, and, for example, less than 0.25 w-ppm, calculated aselemental iron. The hydrotreatment process is any catalytic process,such as a hydrodeoxygenation process performed using a trickle-bedreactor, in which, for example, glyceride oil material is treated withhydrogen to form hydrocarbons. Hydrodeoxygenation can be performed undera pressure from 10 to 150 bar, at a temperature of from 200 to 400° C.and using a hydrogenation catalyst containing metals from Group VIIIand/or VIB of the Periodic System. For example, the hydrogenationcatalysts are supported Pd, Pt, Ni, NiMo or CoMo catalyst, the supportbeing alumina and/or silica. Exemplary catalysts are NiMo/Al2O3 andCoMo/Al2O3.

In order to improve the properties, especially the cold flow properties,of the formed hydrocarbons, the hydrotreatment step can be followed byan isomerisation step. In the isomerisation step the hydrocarbonsundergo an isomerisation reaction whereby isoparaffins are formed.

A rapid increase in the pressure drop of the hydrotreatment reactor wasnoticed to occur in large scale production facilities. The reactor wasopened and a substantial amount of dust-like particles was found insidethe reactor. The dust-like particles were believed to be the cause ofthe plugging and increase in pressure drop over the catalyst bed.Analyses of dust-like particles revealed metals originating fromfeedstock (mainly Fe, Ca, Mg, Na) as well as phosphorus and carbon.Introducing less contaminated feedstock into the process hasdramatically decreased the rate of pressure drop increase in thehydrotreating reactor. The plugging phenomenon was studied in moredetail with a set of laboratory reactor experiments illustrated in theexamples.

Based on the experiments with palm oil having very low level ofimpurities, a catalyst cycle length based on catalyst deactivation withpure feedstock can be calculated. Furthermore, based on plant operatingexperience the rate of reactor plugging can be correlated with ironcontent. From this information, it can be concluded that bio-basedfeedstock (glyceride oil) to be used as feed material for hydrotreatmentreaction can be purified to iron content of less than 1 to 0.2 w-ppm(depending on the dimensioning design WHSV of the hydrodeoxygenationreactor and expected life cycle of the catalyst), for example, in ordernot to shorten the catalyst cycle length due to pressure drop increase.For efficient and profitable plant operation, the Fe content of thefeedstock of the hydrogenation reactor can be less than 0.5 w-ppm, forexample, less than 0.25 w-ppm (w-ppm refers here to ppm by weight). Thispurification result can be obtained (depending on used feedstock) usingpre-treatment methods, such as degumming and bleaching, or alternativelynew pre-treatment technologies or a combination thereof. Thus, disclosedis a glyceride oil intermediate, which intermediate consists ofglyceride oil from at least one renewable source and the iron content ofsaid glyceride oil is less than 1 w-ppm calculated as elemental iron,for example, less than 0.5 w-ppm and, for example, less than 0.25 w-ppm.

EXAMPLES

Undiluted glyceride oil was fed with high WHSV (8-10) through a bedconsisting of hydrotreatment catalyst diluted in 1:2 ratio with quartzsand. Sand dilution was estimated to act as a filter, magnifying theplugging effect of the dust-like particles. This setup enabled reactorplugging to occur in days rather than months as in a reactor on anindustrial scale plant. The reactor was considered to be plugged when apressure drop of 3 bar was reached across the reactor, initial pressurebeing 0.5 bar.

First, a reference run (plant reference run) was conducted with degummedpalm oil as the glyceride oil feed having rather high level ofimpurities (Experiment 1). Experiment 1 was repeated (Experiment 2).This test was repeated without any catalyst to demonstrate the effect ofpresence of catalyst in reactor plugging (Experiment 6). Experimentswere then continued with bleached palm oil having very low levels ofimpurities (Experiment 3), filtered animal fat with high levels of P andNa but almost no other metals (Experiment 4), and finally bleachedanimal fat with moderate levels of P and Fe but almost no other metals(Experiment 5).

A summary of the conducted experiments is shown below:

-   Plant reference run with degummed palm oil (Experiment 1)-   Repetition of experiment 1 with degummed palm oil (Experiment 2)-   A run with bleached palm oil (Experiment 3)-   A run with filtered animal fat (Experiment 4)-   A run with bleached animal fat (Experiment 5)-   A run with degummed palm oil repeated without catalyst (Experiment    6)

The composition of the dust-like particles was determined and the amountof the dust-like particles was measured after the experiment byseparating the quartz sand and dust-like particles from the catalyst byscreening and analysing the sand+dust mixture with wave lengthdispersive a X-ray fluorescence spectrometer (Bruker AXS S4 Explorer),with helium as measurement atmosphere.

The results of the analyses in the experiments are shown in followingTable 1.

TABLE 1 Total increase in pressure drop, total cumulative feed throughreactor; feed impurity levels, impurities found in catalyst, impuritiesfound in sand + dust Experiment No. 1 2 3 4 5 6 Initial dP/bar 0.55 0.620.62 0.62 0.61 0.59 Final dP/bar 3.8 2.9 2.5 1.6 4.44 1.0 delta(dP)/bar3.25 2.28 1.88 0.98 3.83 0.41 Cumulative 31.8 31.6 10.27 25.3 22.6 28.9feed kg Plugging rate 102.1 72.1 18.3 38.8 169.7 14.2 mbar/kgfeed Feedimpurity concentrations P/ppm 3.8 3.7 0.6 24 5.7 3.8 Ca/ppm 1.2 1.1 0.30.6 0.1 1.2 Fe/ppm 1.2 1.3 0.6 0.1 1.8 1.2 Na/ppm 1 0 0 6 0 1 Mg/ppm 0.20 0 0.3 0.2 0.2 Impurities found in sand + dust P/mg 425 309 154 154 309301 Ca/mg 77 77 4 4 0 6 Fe/mg 116 116 77 54 174 18 Na/mg 77 39 0 54 0 6Mg/mg 0 0 0 4 0 0 Impurities found in catalyst P/mg 60 50 20 206 30Ca/mg 10 7 5 1 0 Fe/mg 30 22.5 85 14 70 Na/mg 10 12 5 13 0 Mg/mg 0 0 0 00The pressure drop correlated with cumulative feed in each Experiment ispresented in FIG. 1.

The absolute amounts of individual impurities in the dust-like particleswere then correlated with the absolute pressure drop increases incorresponding experiment. Results are shown as correlation plots withR2-values for P and Fe in FIG. 2 and for all measured impurities inTable 2 below.

TABLE 2 Correlation between absolute increase in pressure drop andabsolute masses of impurities found in dust Impurity R² P 0.27 Ca 0.12Fe 0.93 Na 0.01 Mg 0.18

A relative plugging rate can be calculated for each experiment bydividing the increase in pressure drop with total cumulative feedintroduced in the reactor throughout the experiment. Correlating thisplugging rate with impurities in corresponding feedstocks gives theplots shown in FIG. 3 for P and Fe. This correlation for all measuredimpurities is shown in table 3. The experiment without catalyst isexcluded from FIG. 3, due to different rate of dust formation with andwithout catalyst.

TABLE 3 Correlation between rate of increase in pressure drop (inbar/kg(feed) and concentrations of impurities in feed. Impurity R² P0.04 Ca 0.02 Fe 0.75 Na 0.14 Mg 0.10

According to these results, iron is the only impurity in the dustcorrelating strongly with the increase in pressure drop over thecatalyst bed.

It will be appreciated by those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. The presently disclosedembodiments are therefore considered in all respects to be illustrativeand not restricted. The scope of the invention is indicated by theappended claims rather than the foregoing description and all changesthat come within the meaning and range and equivalence thereof areintended to be embraced therein.

What is claimed is:
 1. A method for avoiding catalyst plugging thatcauses an increase in a pressure drop of a hydrotreatment reactor duringhydrotreatment comprising: purifying a biological feedstock from atleast one renewable source to lower a content of impurities therein,which have a correlation between (a) and (b) greater than 0.14, wherein(a) is a rate of increase in the pressure drop measured as bar/kg ofbiological feedstock and (b) is a respective concentration of eachimpurity measured in ppm, wherein the concentration of each impuritywith the correlation greater than 0.14 is lowered to a value between0.25 to 1 w-ppm; hydrotreating the purified biological feedstock from atleast one renewable source with a catalyst to form hydrocarbons during acatalytic reaction in a trickle bed reactor; and avoiding plugging ofthe catalyst used in hydrotreating that causes an increase in thepressure drop of the hydrotreatment reactor.
 2. The method according toclaim 1, wherein the correlation is 0.75 or greater.
 3. The methodaccording to claim 1, wherein the concentration of each impurity of thefeedstock with the correlation greater than 0.14 was above 1 ppm beforepurification.
 4. The method according to claim 1 or 3, wherein theimpurities of the feedstock with the correlation greater than 0.14include iron.
 5. The method according to claim 1, wherein theconcentration of each impurity of the feedstock with the correlationgreater than 0.14 is lowered to a value between 0.25 to 0.5 w-ppm. 6.The method according to claim 1, wherein the biological feedstock isselected from the group consisting of rapeseed oil, colza oil, canolaoil, tall oil, sunflower oil, soybean oil, hempseed oil, cottonseed oil,corn oil, olive oil, linseed oil, mustard oil, palm oil, peanut oil,castor oil, coconut oil, camellia oil, jatropha oil, an oil derived froma microbial source, animal fat, fish oil, lard, tallow, train oil,recycled fat from the food industry, and a mixture thereof.
 7. Themethod according to claim 1, wherein the hydrocarbons formed in thehydrotreating are further processed in a hydroisomerisation process toiso-paraffins.
 8. The method according to claim 6, wherein the microbialsource is algae, bacteria, molds, filamentous fungi or a combinationthereof.
 9. The method according to claim 1, wherein the hydrotreatingis hydrodeoxygenation performed under a pressure from 10 to 150 bar, andat a temperature of from 200 to 400° C.
 10. The method according toclaim 1, wherein the catalyst comprises Pd, Pt, Ni, NiMo or CoMo, and asupport of alumina and/or silica.
 11. The method according to claim 1,wherein the catalyst comprises a NiMo/Al₂O₃ catalyst, a CoMo/Al₂O₃catalyst, or a combination thereof.
 12. The method according to claim 7,wherein the iso-paraffins are converted into components for use inproducts selected from the group consisting of a base oil, lubricationoil, heating oil, diesel fuel, gasoline, liquefied petroleum gas,aviation fuel, solvent and biogas.
 13. The method according to claim 1,wherein the purified biological feedstock has a phosphorous content thatis greater than 5 w-ppm calculated as elemental phosphorous.
 14. Themethod according to claim 2, wherein the impurities of the feedstockwith the correlation of 0.75 or greater include iron.